Legal AI Models, Retrieval, and Agents

From Chinese legal foundation models and user-centric evaluation to generative retrieval, agentic reasoning, and continuously improving legal AI systems.

Legal foundation models to Legal AI within a Loop
HanFei-1.0UCL-BenchLegal-R1GenArtIDLegal AgentsLoop Engineering
CUHK-Shenzhen and FaDaFu Legal AI Joint Laboratory signing ceremony

The team has built a systematic Legal AI foundation spanning domain-model training, real-user evaluation, legal knowledge retrieval, and agentic evidence-based reasoning. The research has evolved from training a Chinese legal model to connecting models, legal databases, tools, benchmarks, and lawyer workflows in a continuously improving closed loop.

Research Evolution

Model
HanFei-1.0: build legal domain capability

A 7B Chinese legal model trained on approximately 60 GB of cases, statutes, complaints, and legal news, supporting legal question answering, dialogue, and document generation.

User
UCL-Bench: evaluate what legal professionals need

Moves from knowledge-centric legal exams to user-centric evaluation with five legal scenarios and 22 tasks grounded in surveys and validation by legal professionals.

Retrieve
GenArtID: generate statutory identifiers

Reframes legal retrieval as direct prediction of relevant article identifiers, connecting a legal question to structured statutory memory instead of relying only on embedding similarity.

Agent
Legal-R1: retrieve evidence while reasoning

Extends one-shot RAG into a Think → Retrieve → Rethink → Retrieve → Answer process that actively identifies missing evidence and revises reasoning.

Loop
Legal AI within a Loop

Connect real lawyer use, expert edits, data accumulation, benchmark updates, and model training into a sustainable improvement cycle.

Four Research Foundations

2023
HanFei-1.0

Early full-parameter Chinese legal LLM work covering corpus construction, continual pre-training, instruction tuning, and deployment.

Repository
NAACL
UCL-Bench: A Chinese User-Centric Legal Benchmark

Findings of NAACL 2025, pp. 7960–8003. It asks whether a model can complete the work legal professionals actually need.

Paper
ARR
Legal-R1: Agentic Retrieval for Evidence-Based Legal Reasoning

Combines legal agents, databases, iterative retrieval, and traceable evidence in a multi-step reasoning process.

OpenReview
ARR
GenArtID: Generative Article Identifier Prediction

Uses the structure of statutory knowledge to retrieve law through article identifiers rather than only vector matching.

OpenReview

Harness → Benchmark → Training → Loop

Harness

Connect legal databases, case repositories, contracts, knowledge graphs, retrieval interfaces, and reusable Legal Skills so agents can act in real workflows.

Benchmark

Derive tasks from lawyer practice and involve legal professionals in rubric design, expert evaluation, and authoritative validation.

Training

Use expert edits and evaluation data for supervised fine-tuning, rubric-based reinforcement learning, and legal retrieval training.

Data Flywheel

Turn adoption, modification, scoring, and business outcomes into new training data and benchmark updates.

Model building → evaluation → workflow automation → real-user pilots → data feedback and iteration. This is the core Loop Engineering path for reliable, explainable, and trustworthy Legal AI.

Joint Laboratory and Real-World Agenda

  • Core research: legal reasoning, hallucination reduction, factual evidence chains, privacy, and security.
  • Priority scenarios: intelligent contract review, enterprise compliance and risk control, and public legal services.
  • Operating model: university-led frontier research plus enterprise-led scenario validation and productization.

Why It Matters

The next step is not another isolated legal LLM. It is a Legal AI system in which models, structured legal knowledge, tools, benchmarks, expert feedback, and real lawyer workflows improve together.